The final curtain?

Alex Cooke of Kingspan Light + Air looks at why polycarbonate curtain walling solutions are being specified as an alternative to glass across various building types

Glittering glazed buildings are a popular sight in many of our towns and cities. Whether they house offices, homes, shops, healthcare, education facilities or public spaces, curtain wall facades are a popular design choice for projects looking to increase internal daylight levels, offer external or even internal views, and present a clean, contemporary overall aesthetic. However, glass-based systems can present challenges both onsite and during operation and therefore may not be suitable for every building. Polycarbonate may offer a viable alternative that resolves these dilemmas.

Why polycarbonate?

Used in everything from car parts and bicycle helmets to riot shields and bullet-proof glass, polycarbonate is one of the most widely used engineered materials in the world. However, it is when it is applied to glazing that its architectural design potential is really illustrated to the full.

Polycarbonate is celebrated for its extreme impact resistance and long-lasting durability. As a glazing product, these properties are not only beneficial during transportation and installation but also when it is in use, safeguarding against extreme weather, falling branches and vandalism. It is also often formulated to retain its translucency for the lifetime of the product, ensuring it does not degrade, discolour, or lose its excellent light transmission properties. Typically a fraction of the weight of glass, it offers clear structural benefits whilst being easy to handle and install, improving onsite safety and speed of build.

Of course, without consideration, high levels of light transmission can lead to issues with solar heat gain or visual glare. To resolve this, polycarbonate products can be manufactured using prismatic layers to diffuse incoming light, creating a uniform illumination that avoids hot spots and enhances visual acuity. Formulations are also available with additives that reflect infrared (IR) radiation and coloured tints can also be added to give architects more design options.

Polycarbonate is also one of the few materials that can be completely recycled at end of life and remanufactured to create a range of new products with no loss of material quality. This makes it an ideal material to choose for projects seeking to be more sustainable.

Thanks to these properties, we are seeing it commonly used in standard daylighting products such as rooflights. However, modern vertical wall light solutions are now emerging in the market, showing how polycarbonate can be used to create real architectural impact in the form of sleek, modern designs.

What comprises a unitised translucent polycarbonate wall system?

Unitised translucent polycarbonate wall systems have been designed specifically for buildings where providing daylighting without glare or reduced thermal performance is key. They consist of double-skin, dense-cell polycarbonate insulated panels that are joined by a mechanically interlocking aluminium structure that eliminates the need for wet seals and adhesives. These units are designed to provide excellent light transmission of up to 33% and U-values as low as 0.49 W/m2K. They can also be supplied with additional acoustic or thermal performance enhancing insulation where required.

These systems can be used to create a variety of glazing features, such as clerestory bands along the top of a space, to create sightlines or intermittent/targeted views, or even for full ‘light-box’ style applications. The panels are scalable and able to span long distances between supports with minimal visible substructure and a wide range of skin colours and combinations. This gives architects complete creative freedom to design unique and striking facades, especially when used in conjunction with backlighting, adding drama and presence even if the building is not in use.

Due to the way they are fixed, these systems can also benefit from Removable Skin Technology (RST). This enables just the outer skin of the system to be removed and replaced, providing easy future renovation or repairs throughout the building’s lifecycle. As it is mostly made from polycarbonate and aluminium, the system components can be recycled at end of life.

These polycarbonate wall systems have proven success in the USA, where they have been used on projects in sectors such as education, public sector, sport and leisure, offices, and even industrial buildings. Below is one example, from education.

Case study: Eagle Centre Public Charter School, Washington DC

Home to more than 900 students, the Eagle Centre is the first early childhood public charter school in Washington DC. Its design aimed to create an intellectually stimulating environment with excellent sustainable credentials. Meanwhile, the urban city location also meant physical security was crucial, and vandalism prevention was a key concern.

Shinberg Levinas Architectural Design specified over 1,200 m2 of Kingspan UniQuad 120 unitised translucent curtain walling system for the project. The facades were designed without any exposed aluminium connectors and included blue and white panels to reflect the school colours. The outside panels were matte finished for added security and daytime privacy.

“We picked a system that would give them the daylight they wanted without having to use windows. The UniQuad 120 provides an interesting effect inside, durable material, and a great aesthetic,” explained project architect Carlos Talero. Additionally, the panels’ Removable Skin Technology (RST) allows the exterior panel to be replaced as needed in the event of vandalism.

The project received LEED Gold, with the UniQuad 120 supporting the achievement of points for both daylighting and glare control. Its excellent airtightness and weatherproofing were also key benefits for the project, protecting the internal environments from draughts and water ingress.

Alex Cooke is managing director at Kingspan Light + Air UK and Ireland